The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
With the aim of lightening a turbo machine, certain of its components that are conventionally produced from metal may be produced from a composite material. Structural components such as supports and casings may be produced from a composite material. In particular, an external casing of a compressor, in particular low pressure, may be produced from a composite material.
Such a casing generally has a cylindrical portion which supports annular rows of blades, and annular mounting flanges which extend radially. The flanges permit the assembly of the compressor casing on an intermediate blower casing, and the mounting of an annular separation nose. The internal surface of the casing permits the annular flow to be guided along the compressor, and must have a smooth surface for this purpose, without projections. This constraint requires sharp edges to be produced in the area of the mounting flanges.
A composite external casing of a compressor may be produced from a preform densified by a matrix. The preform may be formed by a stack of fibrous sheets stacked one on top of the other, the sheets extending both over the cylindrical portion and over the mounting flanges. Once positioned in the mould, the preform is arranged in an injection mould having edges intended to reproduce the desired form of the casing. The stacked preform forms a rounding in the area of the edge of the mould and leaves an empty space in this location. In the course of the injection, the space is occupied by the resin without being reinforced by fibers. Consequently, the composite casing has a weakness in this location.
Document GB 2486231 discloses a tool for the shaping of a preform of a composite casing for a turbo machine, the casing having radial annular flanges at its upstream and downstream extremities. The preform comprises a stack of folds which are formed in the shaping tool, in such a way as to produce the annular flanges. In order to limit the appearance of rounding of the preform beneath the flanges during its shaping, the tool comprises mobile blocks forming the flanges, the preform being arranged beforehand in a membrane in which aspiration is created. This approach makes it possible to come closer to a desired geometry, although it does require expensive tooling. Furthermore, the rounding occupied by the preform depends on the thickness of the lower fold. The rounding can be distorted because of the aspiration.
Document EP 1 900 502 A1 discloses an annular composite component of a turbo machine. The component has an annular body and annular flanges at its extremities, and annular sharp edges in the interior of the flanges. The composite component comprises a plurality of fibrous reinforcements, one of which is frayed in the area of the edges in such a way as to distribute the fibers there in the junctions between the flanges and the annular body. The approach of this document makes it possible to distribute fibers in the junctions, but gives rise to heterogeneity in the density of the fibers. This heterogeneity reduces the mechanical strength of the composite component, and in particular in response to a bending effort applied to a flange.